When initiated in 1990, the specific aims of this project were to assess the T cell proliferative response to hepatitis C antigens during the course of acute hepatitis C virus (HCV) infection and determine whether specific patterns or levels of T cell responses correlated with disease outcome. This objective was based on the hypothesis that in the course of hepatitis C infection, as previously observed during hepatitis B infection, the development of T cell responses to specific viral proteins would closely correlate with resolution of acute viral hepatitis and clearance of viral infection. As understanding the nature of hepatitis C infection and liver disease has grown over the past 7 years these specific aims have been modified to encompass broader attempts to follow antibody responses to various hepatitis antigens during the evolution of hepatitis C infection and to characterize the nature of acute hepatitis cases previously classified as acute non-A, non-B hepatitis.